Add null check to fileio demo 4

Author: mateoconlechuga

CEdev/examples/library_examples/fileio/demo_4/bin/FILEIO4.8xp

@@ -27,13 +27,12 @@ void main(void) {
 	int in;
 
 	/* Get the answer variable */
-	if(ti_RclVar(TI_REAL_TYPE, ti_Ans, &real_in))
-		return;
-	
-	if((in = os_RealToInt24(real_in)) < 1)
-		return;
+	if(ti_RclVar(TI_REAL_TYPE, ti_Ans, &real_in)) return;	
+	if((in = os_RealToInt24(real_in)) < 1) return;
 
 	prime_factors((unsigned)in);
+	
+	if(!total_primes) return;
 	list_out = ti_MallocList(total_primes);
 
 	for(i=0; i<total_primes; i++) {